As Central Subway construction continues to bore it's way from AT&T Park to Chinatown, the San Francisco County Transportation Authority and the Municipal Transportation Agency are proposing another subterranean transit solution for the slow-plodding M-Ocean View line along 19th Avenue.

After a feasibility study, the two agencies are recommending the M-Ocean View head underground near St. Francis Circle and pass by two new underground stations at Stonestown Galleria and S.F. State, which will reduce travel times by 35 to 45 percent and free up space on the surface roads for bus loading or bike paths. Besides sliding under the mess of traffic on 19th Avenue, where the M-line averages a leisurely eight or nine miles per hour, a subway would save students, shoppers and commuters the hassle of crossing three lanes of traffic to get to the Muni Metro platforms in the median.

According to the study, the project would cost anywhere from $520 million to $780 million (or even higher as transit projects are rarely under budget). The project could be completed by 2022, assuming funding is secured. At the moment there's a $1.8 million commitment from S.F. State to help pay for a new station and the developers behind the re-designed Parkmerced complex are also on board. In general, any improvements to the line will be necessary if the area is to get any more dense.

Speaking of Parkmerced, the development plans call for a new Muni Metro station inside the neighborhood complex, which will require another study entirely. And finally, for an additional $200-300 million, the SFMTA could extended the M-Ocean View all the way to meet BART at the Daly City Station.